update ratatui dependency to 0.30 (#24504)

# Objective

Ratatui is used by the `tools/export-content` crate. Update it to its
latest stable version.

This PR supersedes #22351 which is a dependabot PR that got stuck on
some breaking changes in ratatui 0.30.

## Solution

Ratatui's `Backend` type now has an associated `Error` type that does
not specify `Send + Sync`,
which is a bit awkward because `miette` requires those. Fixed by adding
the requirements locally,
and changing `init_terminal()` to return its specific backend type so
that the compiler can verify its `Error` type.

## Testing

Ran the tool before and after and it looked the same.